With the continuous evolution of wireless communication technologies and protocol standards, the mobile packet service has been developed tremendously, and the data throughput capacity of a single terminal is on the rise. Take the Long Term Evolution (referred to as LTE) system for example, the maximum downlink rate for data transfer supported in the 20M bandwidth is 100 Mbps; in the subsequent LTE Advanced system, the data transfer rate can be further enhanced, even up to 1 Gbps.
The expansive growth of terminal data traffic makes the existing network resources gradually inadequate, especially in the case the new generation of communication technologies (such as 3G, LTE) cannot widely cover the whole network, followed by a problem that the user demands for rate and flow cannot be met, the user experience becomes worse. How to prevent and change this situation is a matter that operators must take into account, on the one hand, it needs to accelerate new technology promotion and network deployment; on the other hand, it desires to be able to strengthen the existing networks and technologies to achieve the purpose of rapidly improving the network performance. As we all know, in addition to the wireless network technology provided in the 3rd Generation Partnership Project (referred to as 3GPP), the currently widely used Wireless Local Area Network (referred to as WLAN), particularly the WLAN based on IEEE802.11 standard has been widely used in hotspot access coverage in homes, enterprises and even the Internet. Among them, the technical specifications proposed by the WIFI Alliance is most widely used, thus the WIFI network in practice often equals to the WLAN based on the IEEE 802.11 standard.
On this premise, each operator and company have proposed to integrate the WLAN with the existing 3GPP access network, to achieve joint transmission, so as to achieve the purpose of offloading the load and improving the network performance. For example, in earlier versions of the standards, the 3GPP has developed the related 3GPP access network and WLAN Interworking protocols, the interworking architecture relies on that the operators have independent 3GPP access network and independent and complete WLAN, data flows of these two networks need to go through the 3GPP core network elements. There is also such as the network convergence solution, similar to the carrier aggregation, proposed by Intel, and in this integration architecture, the 3GPP and the WLAN are still two separate access networks, but the WLAN only exists as a data connection transmitted between the access network and the User Equipment (referred to as UE) in the existing 3GPP access network, and the main management of the access network for the UE and a part of the possible user data are transmitted in a connection based on the 3GPP access network. It can be seen that, no matter in which joint transmission scheme, the UE needs to respectively access to the two separate access networks: 3GPP and WLAN (a network element in a 3GPP access network and WLAN access point).
However, in the related art, since the UE needs to scan the WLAN frequency band to detect whether there is an available WLAN or not, it takes long time for said UE accessing to the WLAN (currently the time for said UE accessing to the 3GPP access network is millisecond, and the time for accessing to the WLAN is at the level of seconds), thus taking a long time for the UE residing in/connected to the 3GPP cell accessing to an available WLAN (said available WLAN specifically refers to the WLAN deployed by the operator who deploys the 3GPP access network, or the WLAN which can work with said 3GPP access network to execute services such as data joint transmission) and obtaining the subsequent data joint transmission and/or other services, thus the user experience is not good.